Tracheata a term used as the name of a group of animals, including all those which breathe by means of tracheae - viz., minute tubes ramifying through the body and opening to the exterior. The group would include the Protracheata - i.e. Peripatus (q.v.) - the Myriapods (Centipedes and Millepedes), the Insects, and Arachnidae. It is doubtful, however, whether the tracheae in these four classes are developed in the same way, while many of the Arachnidae, such as Limulus (the King Crab), breathe by gills, and not tracheae. The name is not, therefore, generally adopted.